July 4, 2012

New Particle Discovery Could Be The Elusive Higgs Boson

by editor

Lawrence LeBlond for redOrbit.com - Your Universe Online

The Fourth of July is a day of celebration for millions of people all across America, celebrating the birth of a nation. But in Geneva, Switzerland, a much different celebration is occurring as scientists at Europe´s CERN research center have revealed the discovery of a new subatomic particle, one that could be the elusive Higgs boson or “God particle.”

The revelation was made at a seminar held at CERN today (July 4) in Geneva. But despite a roomful of cheers and standing ovations, the CERN scientists said more data will be needed to confirm whether it is indeed the much looked for Higgs Boson -- the particle believed to be the main building block for the universe.

“We have reached a milestone in our understanding of nature,” CERN director general Rolf Heuer told a gathering of scientists and the world´s media near Geneva on Wednesday. “The discovery of a particle consistent with the Higgs boson opens the way to more detailed studies, requiring larger statistics, which will pin down the new particle's properties, and is likely to shed light on other mysteries of our universe.”

The new particle was confirmed by two separate experiments (ATLAS and CMS) both presenting their latest preliminary results at the seminar, which is considered a curtain raiser to the year´s major particle physics conference (ICHEP2012) being held in Melbourne, Australia. Both experiments observed the new particle in the mass region around 125 to 126 GeV (gigaelectronvolts).

The hunt for the elusive Higgs boson has been a long and winding road, first theorized more than 50 years ago. And today, physicists might be on the doorstep of perhaps the greatest discovery in particle physics in history. The Higgs is the final building block that has been missing from the “Standard Model,” which describes the structure of matter in the universe.

Scientists from the Weizmann Institute in Rehovot, Israel, have been prominent partners in the hunt for the Higgs from the early days. Professor Giora Mikenberg was head of the research group that searched for the God particle in CERN´s OPAL experiment for many years. He then went on to head the ATLAS Muon Project -- one of the two experiments that revealed the newest particle discovery.

Professor Ehud Duchovni is leader of the Weizmann team that examines other key questions at CERN. And Weizmann´s Professor Eilam Gross is currently the ATLAS Higgs physics group convener.

“This is the biggest day of my life. I have been searching for the Higgs since I was a student in the 1980's. Even after 25 years, it still came as a surprise. No matter what you call it — we are no longer searching for the Higgs but measuring its properties. Though I believed it would be found, I never dreamed it would happen while I was holding a senior position in the global research team,” said an ecstatic Prof. Gross at the seminar.

“It´s hard not to get excited by these results,” said CERN Research Director Sergio Bertolucci. “We stated last year that in 2012 we would either find a new Higgs-like particle or exclude the existence of the Standard Model Higgs.”

“With all the necessary caution, it looks to me that we are at a branching point: the observation of this new particle indicates the path for the future towards a more detailed understanding of what we´re seeing in the data,” he added.

But even as the rumors begin to fly through the media world, the physicists at CERN are quietly cheering.

“Without a doubt, we have a discovery,” said an anonymous team member working on the ATLAS project. “It´s pure elation!”

Named after Scottish theoretical physicist Peter Higgs, who first theorized the particle in the 60s, the Higgs boson is the one particle that ties all other particles together and confirming its existence will be huge for particle physics.

Higgs, who was invited to attend the seminar, was clearly overwhelmed. With eyes brimming, he addressed fellow researchers: “It is an incredible thing that it has happened in my lifetime.” Yet, even with all the excitement, he acknowledged it was still too early to confirm the findings as the missing building block of the universe.

But, he told the audience, the discovery of something that appears to be so close to what he predicted, is by no means small scale, calling the finding a huge achievement for the Large Hadron Collider built in a 17-mile underground tunnel on the French-Swiss border.

The $10 billion atom smasher has been creating high-energy collisions of protons to investigate dark matter, antimatter and the creation of the universe (the Big Bang). The LHC accelerates these beams of protons up to nearly 100 percent the speed of light, increasing their mass by 7,500 times that of their normal resting mass. The accelerator aims the beams straight toward each other, causing collisions that release so much energy, the protons themselves explode. For even less than the blink of an eye, the conditions similar to those that existed in the universe in the fraction of a second after the Big Bang are present in the accelerator.

But the likelihood of creating the Higgs in a single collision would be similar to trying to find a needle in a haystack, as the saying goes.

To cope with this task, the Weizmann scientists developed unique particle detectors, which were manufactured at the Institute, and in Japan and China. These detectors have been adapted to detect muon particles. In some of the very rare collisions that produce the footprint of the Higgs particle is four energetic muons. Thus, the detection of such muons provides circumstantial evidence for the existence of the Higgs particle.

Scientists from both the ATLAS and CMS experiments analyzed data from a thousand trillion proton collisions, in which the teams found evidence that suggests the Higgs really exists. The evidence to suggest this existence arises through searches for anomalies in the collected data, along with, and in comparison to, expected data if such a particle does not exist.

This search focuses on the estimated mass of the particle: 126 trillion GeV. When the scientists do manage to find such anomalies, they must then rule out the possibility that it is due to statistical fluctuation.

The calculations carried out by scientists in recent weeks, ones in which Prof. Gross played a key role, have revealed with a high degree of certainty, that the newly discovered particle has mass similar to the expected mass of the Higgs boson. But scientists are stopping short of saying ℠yes, this is the Higgs,´ due to the possibility that it could be a separate boson particle, found within the Higgs´ mass range.

With excitement levels on high, physicists cautioned that there is still much to learn.

“We have closed one chapter and opened another,” Peter Knight of Britain´s Institute of Physics told Reuters.

“If I were a betting man, I would bet that it is the Higgs,” added Oliver Buchmueller at CERN. “But we can't yet say that definitely yet. It is very much a smoking duck that walks and quacks like the Higgs. But we now have to open it up and look inside before we can say that it is indeed the Higgs.”

Physicists said they will not announce the discovery of the Higgs until the signal surpasses 5 sigma, meaning that it has just a 0.00003 percent probability that the results is due to chance. Both ATLAS and CMS experiments are seeing signals between 4.5 and 5 sigma, just a smidgen away from a solid discovery claim. Their results are also consistent with analysis from the Tevatron collider, which was presented today at Fermilab in Batavia, Illinois.

The leaders of the two experiments -- Joe Incandela, head of CMS, and Fabiola Gianotti, head of ATLAS -- each presented strong evidence of the new particle at the CERN seminar.

Incandela said it was too soon to say definitively whether it is the "standard model" Higgs. But called it “a Higgs-like particle” and said “we know it must be a boson and it's the heaviest boson ever found.”

Gianotti told the Los Angeles Times that “the standard model is not complete” but that “the dream is to find an ultimate theory that explains everything.” She remarked: “we are far from that.”

Incandela said the last undiscovered piece of the standard model could be a variant of the Higgs that was predicted or something else that entirely changes the way scientists think about how matter is formed.

“This boson is a very profound thing we have found. We're reaching into the fabric of the universe in a way we never have done before. We've kind of completed one particle's story,” he said. “Now, we're way out on the edge of exploration.”